Sodium ions models cheeses at molecular and macroscopic levels

National audience

anglais. The excessive consumption of sodium is one of the causes of nutritional related-health problems. The reduction of salt content without affecting technological and sensorial properties of foodstuffs is currently a challenge for the food industry1. There is a need to develop tools to quantify the “active” sodium ions in food products at molecular and macroscopic levels to better understand in-mouth salt release and flavour perception. In this context, methods for the quantification of the bound fraction were developed: 23Na NMR single-quantum (SQ) and double-quantum-filtered (DQF) sequences at molecular level using Bruker Avance-500 spectrometer equipped with 10 mm probe 2, 3 and applied to cheeses. At macroscopic level, the partition and diffusion coefficients of sodium ions in cheeses were determined according to Lauverjat et al. 4. The partition and diffusion coefficients were calculated after the quantification of sodium by a conductimetric detection, after ionic separation using HPLC (Dionex ICS-3000), or directly with a Na+ specific electrode (ThermoFisher Scientific), respectively. Model cheeses with different structures were made with 3 ratios of lipids/proteins (0.5, 0.75 and 1), and 2 salt concentrations. The 23Na relaxation measurements and the DQF parameters highlighted the impact of the composition (ratio of lipids/proteins) on the interactions between the sodium ions with the food matrices. The differences in bound fraction are related to differences in partition and diffusion coefficients. This study showed the usefulness of 23Na NMR for investigating bound sodium and understanding the role of sodium in foodstuffs. Moreover, partition and diffusion coefficients of sodium helped analysing the impact of sodium in food. The data could be further used to explain the sensory perception.